一个英文句子解释it's really been a while,try again.这里为什么要用been.为什么不用

一个英文句子解释it's really been a while,try again.这里为什么要用been.为什么不用 It's+been++a+long+time.been在这里起什么作用?为什么要用been It's been a while It'S Been A While 歌词 英语：这里为什么要用have been It's been nice talking to you.为什么用is不用has? It's been a while since I left here it's really been a longtime since i went home. 现在完成时这里为什么要加been,什么情况下要加been? He has lived here since 1992.这里为什么用has lived而不用has been livi it's raining again.中为什么不用it was. 英语：这里为什么要用have been 呢